1. Field of the Invention
The present invention relates to an endoscope system permitting expandable combinations of endoscopes, signal processors, and light sources.
2. Description of the Related Art
Endoscopes have been adopted widely in recent years, so that an elongated insertion tube can be inserted into a body cavity to observe organs in the cavity, or a treatment adapter can be routed through a treatment channel, if necessary, to perform various treatments. Endoscopes are used not only for medical but also industrial purposes; such as, observation or inspection of objects in pipes of boilers, machines, or chemical plants, or those in machines.
The aforesaid endoscope may be either an optical endoscope (so-called fiberscopes) permitting observation with naked eyes based on image fiber technologies, or an electronic endoscope having a solid-state imaging device at the tip of an insertion tube to observe subjects on a TV monitor.
An endoscope apparatus having an electronic endoscope requires not only a light source but also a signal processor for driving a solid-state imaging device, and for processing the output signal of the solid-state imaging device to generate a video signal. The endoscope apparatus provides high-resolution images and permits easy image recording and reproduction.
Therefore, electronic endoscopes have taken over from fiberscopes as a mainstream tool of endoscopy nowadays. The core of endoscopic technologies has shifted from image fiber technologies to electronic technologies. More specifically, a semiconducting technology relating to improvement of a charge coupled device (hereafter, CCD) or any other solid-state imaging device, an imaging circuit technology (video process technology) for driving the solid-state imaging device and converting the output signal into a video signal, and a light adjustment technology relating to a light source have become main targets that must be tackled in order to develop endoscope-related technologies.
Under these circumstances, an endoscope apparatus commercialized with state-of-the-art technologies at one point in time rapidly becomes a technologically obsolete because of rapid advancements in the fields of semiconducting, imaging circuitry, and light adjustment. Users who have purchased certain products may be disappointed at finding the debut of a new product or an upgraded version.
Only certain types of signal processors and light sources can usually be combined with certain models of endoscopes due to the differences in the number of pixels of solid-state imaging device and the driving mode, or the difference in color imaging; that is, field sequential or simultaneous (color mosaic) imaging. Even if new products are put on the market, they are nothing but improved versions of previous models. In order to utilize the improved part, users are required to purchase new endoscope apparatuses or keep using existing ones.
To cope with this problem, various proposals have been made to permit the use of the same equipment regardless of the difference in the type of solid-state imaging device or imaging mode. For example, U.S. Pat. Nos. 4,774,568, 4,816,909, 4,891,695, 4,926,258 all disclose endoscopes using different types of solid-state imaging devices. U.S. Pat. Nos. 4,853,773, 4,855,819, Japanese Patent Laid-Open No. 1988-200736, Japanese Patent Laid-Open No. 1988-220837, Japanese Patent Laid-Open No. 1988-304221, and Japanese Patent Laid-Open No. 1990-305543 all disclose related art capable of operating in different imaging modes.
U.S. Pat. No. 4,774,568 discloses an endoscope apparatus in which endoscopes operating the same imaging mode but having different types of solid-state imaging devices can be used. Therein, a connector for connecting between an endoscope and a main unit is provided with an ID detection member for identifying the imaging position of a solid-state imaging device incorporated in an endoscope, and the image format of a reflected image or unreflected image. Depending on the signal the ID detection member detects, it is determined whether the focal position of a solid-state imaging device is set to forward observation, lateral observation, or backward observation, or whether images are displayed laterally or reversely. Thus, formed images are displayed at a correct position on a TV monitor. In U.S. Pat. No. 4,816,909, an endoscope connector is provided with a ROM containing information indicating the number of pixels of a solid-state imaging device and the spectral characteristic for each endoscope. Then, depending on the information read from the ROM, either a drive or processing circuit is selected.
In U.S. Pat. No. 4,891,695, at least one pixel element of a solid-state imaging device in an endoscope is designed to that the area or at least one lateral side will be the same as that of an effective pixel. Thereby, a pixel configuration is detected to control a video signal processing means. U.S. Pat. No. 4,926,258 discloses an endoscope apparatus in which endoscopes having solid-state imaging devices provide different numbers of pixels. Therein, a drive signal containing a horizontal transfer clock with certain frequencies is applied to a solid-state imaging device and then the signal read from the solid-state imaging device is processed to generate a video signal.
On the other hand, U.S. Pat. No. 4,853,773 discloses an endoscope signal processing apparatus, supporting different imaging modes, wherein an endoscopic signal processing unit is equipped with a first signal processor for processing the signal sent from a field sequential type imaging device, and a second signal processor for processing the signal sent from a simultaneous type imaging device. The endoscopic signal processing unit identifies the imaging mode of an endoscope connected, selects a corresponding signal processor, then outputs a video signal. U.S. Pat. No. 4,855,819 discloses an endoscope imaging system in which a field sequential type light source and signal processor, and a simultaneous type light source and signal processor are accommodated in one housing. Connectors are formed for both imaging modes, so that either field sequential type or simultaneous type endoscopes can be used.
Japanese patent Laid-Open No. 1988-20736 discloses an endoscope imaging apparatus in which a common circuit is used as parts of a signal processor for field sequential type color imaging system endoscopes and a signal processor for color mosaic imaging system endoscopes. In Japanese Patent Laid-Open No. 1988-220837, a signal processor for field sequential type color imaging system endoscopes and a signal processor for color mosaic imaging system endoscopes are mutually connectable, so that one of the panels can be used to adjust the gain of the other signal processor.
Moreover, Japanese Patent Laid-Open No. 1988-304221 discloses an endoscope apparatus in which an external TV camera of an endoscope whose image transmission optical system has a final image forming position outside of the main unit is provided with a type signal generation circuit for generating an identification type signal. Depending on the identification type signal sent from the type signal generation circuit, simultaneous or field sequential imaging is determined to select an associated light source and signal processor. Japanese Patent Laid-Open No. 1990-305543 discloses an endoscope in which a user presses a switch to specify whether to adopt simultaneous or field sequential imaging, then a mosaic filter or a light transmission body is arranged by an electrostatic motor on a photosensitive section of a solid-state imaging device depending on the simultaneous or field sequential imaging mode. Then, the identification signal sent from the type signal generation circuit is checked to determine either the simultaneous or field sequential imaging mode, then an associated light source and signal processor are selected.
However, when a means for identifying the type of endoscope is installed, or light sources or signal processors of field sequential and simultaneous imaging modes are prepared, the product becomes so expensive that users have to incur an enormous amount of equipment investment. Besides, the endoscope apparatus becomes very large and heavy.
Even if functions are installed in a single unit or system to cope with different types of endoscopes, all of the functions are not used for normal operation and many functions remain idle. This opposes the concept of effective use of equipment and wastes equipment.
A unit or a function of a system a user is currently using and dissatisfied with differs from user to user. For example, a user may be disappointed with insufficient resolution of endoscopic images, but another user may be annoyed with slow light adjustment or color aberration.
Even if a single unit or system is upgraded, partial improvements in semiconducting technologies relating to improvement of a solid-state imaging device, imaging circuit technologies, or light source light adjustment technologies are not implemented in the unit or system according to needs from users.